Thanks Ian,
NPA-38 is in due process in the JAA; it completed its passage through the Operations Sectorial Team (OST) last week completely
unchanged (from the revised version post consultation) with unanimous agreement. The technical committees have completed their scrutiny and now it passes to the Regulations Committee (RST) who's function is to ensure that 'amendment and consultation' procedures have been conducted in accordance with the appropriate rules (JAR 11). It remains completely harmonised with the concurrent ICAO proposal for revision which is also just completing due process.
Aser, I have mailed you a paper on PC2 offshore which should answer your questions in detail but briefly:
The text that Aser reproduced from Subpart G of JAR-OPS 3 (Performance Class 1) uses language that depends on the formal definition of a Category A procedure - which has been certificated by our Airworthiness colleagues. Whilst those procedures and language may be conducive to onshore procedures at an elevated heliport, they are not flexible enough for offshore operations. They require specific deck sizes (which in most cases are greater than 1D); calculation of obstacle clearance; do not take account of the type of environmental conditions that always seen around helidecks; and do not account for moving decks.
To ensure that there is no confusion between PC1 and PC2e, TDP is replaced by Rotation Point (RP) and LDP by Committal Point (CP) - both of which are defined in Subpart F of JAR-OPS 3; their functions are broadly similar but are not defined in the Approval part of the FM but in the information section, or in the Operations Manual in accordance with the existing guidance in JAR-OPS 3.
Here is some text from NPA-38 (and the revised guidance) which addresses some of the issues:
For a number of reasons (e.g. the deck size, and the helideck environment – including obstacles and wind vectors), it was not anticipated that operations in PC 1 would be technically feasible or economically justifiable by the projected JAA deadline of 2010 (OEI HOGE could have provided a method of compliance but this would have resulted in a severe and unwarranted restriction on payload/range).
However, due to the severe consequences of an engine failure to helicopters involved in take-off and landings to helidecks located in hostile sea areas (such as the North Sea or the North Atlantic), a policy of Risk Reduction is called for. As a result, enhanced Class 2 take-off and landing masses together with techniques that provide a high confidence of safety due to: deck-edge avoidance; and, drop-down that provides continued flight clear of the sea, are seen as practical measures.
For helicopters which have a Category A elevated helideck procedure, certification is satisfied by demonstrating a procedure and adjusted masses (adjusted for wind as well as temperature and pressure) which assure a 15ft deck edge clearance on take-off and landing. It is therefore recommended that manufacturers, when providing enhanced PC2 procedures, use the provision of this deck-edge clearance as their benchmark.
As the height of the helideck above the sea is a variable, drop down has to be calculated; once clear of the helideck, a helicopter operating in PC1 would be expected to meet the 35ft obstacle clearance. Under circumstances other than open sea areas and with less complex environmental conditions, this would not present difficulties. As the provision of drop down takes no account of operational circumstances, standard drop down graphs for enhanced PC2 - similar to those in existence for Category A procedures - are anticipated.
Under conditions of offshore operations, calculation of drop down is not a trivial matter - the following examples indicate some of the problems which might be encountered in hostile environments:· Occasions when tide is not taken into account and the sea is running irregularly - the level of the obstacle (i.e. - the sea) is indefinable making a true calculation of drop down impossible.
· Occasions when it would not be possible - for operational reasons - for the approach and departure paths to be clear of obstacles - the ‘standard’ calculation of drop-down could not be applied.
Under these circumstances, practicality indicates that drop-down should be based upon the height of the deck AMSL and the 35ft clearance should be applied.
There are however, other and more complex issues which will also affect the deck-edge clearance and drop down calculations:· When operating to moving decks on vessels, a recommended landing or take-off profile might not be possible because the helicopter might have to hover alongside in order that the rise and fall of the ship is mentally mapped; or, on take-off re-landing in the case of an engine failure might not be an option.
Under these circumstances, the Commander might adjust the profiles to address a hazard more serious or more likely than that presented by an engine failure.
It is because of these and other (unforeseen) circumstances that a prescriptive requirement is not used. However, the target remains a 15ft deck-edge clearance and a 35ft obstacle clearance and data should be provided such that, where practically possible, these clearances can be planned.
As accident/incident history indicates that the main hazard is collision with obstacles on the helideck due to human error, simple and reproducible take-off and landing procedures are recommended.
In view of the reasons stated above, the future requirement for PC 1 is replaced by the new requirement that the take-off mass takes into account: the procedure; deck-edge miss; and drop down appropriate to the height of the helideck. This will require calculation of take-off mass from information produced by manufacturers reflecting these elements. It is expected that such information will be produced by performance modelling/simulation using a model validated through limited flight testing.
Jim